Recently, solid-state image sensing devices have come to be used in image input apparatuses such as digital cameras, video cameras and image readers. As such solid-state image sensing devices, there are CCD image sensors as well as such non CCD-type image sensors as bipolar transistor-type image sensors, field effect transistor-type image sensors and CMOS image sensors. With such image input apparatuses, optical image information (an optical image) is converted into electrical signals by a photoelectric converter and the converted electrical signals are signal-processed and displayed on a display unit, recorded on a storage medium, and so forth.
To obtain a higher performance solid-state image sensing device, it is desirable to reduce the surface area (pixel surface area) of the light-receiving surface of the photoelectric conversion element that is the photoelectric converter that actually converts the optical image into electrical signals and increase the number of photoelectric converter elements deployed, while at the same time reducing the solid-state image sensing device chip size.
However, with continued advances in high-density pixel integration and chip size reduction, the quantity of light that a single photoelectric converter element which constitutes a pixel can receive decreases as the surface area of the light-receiving surface decreases, and thus decreasing the sensitivity of the device. To remedy this situation, a technology is known that reduces the decrease in sensitivity by forming a microlens on a flattened protective film provided on the light-receiving surface and concentrating incoming light on the light-receiving surface.
In addition, with the demand for even further high-density pixel integration and chip size reduction, the need to provide an inner lens between the microlens and the photoelectric converter element, composed of a film having a refractive index different from those of the adjacent layers, increases.
For example, Japanese Patent Application Laid-Open No. 2005-012189 discloses a solid-state image sensing device having a microlens and an inner convex lens. A brief description is given of the configuration of the solid-state image sensing device disclosed in Japanese Patent Application Laid-Open No. 2005-012189 using FIG. 15.
In FIG. 15, reference numeral 13 indicates a semiconductor member, 1 indicates photoelectric converter elements formed within the semiconductor member and 2 represents an element separation area. Reference numeral 4 indicates a first wiring pattern and 6 indicates a second wiring pattern, with the first wiring pattern 4 and the second wiring pattern 6 separated by a first dielectric 3 and a second dielectric 5. A third dielectric 7 above the second wiring pattern 6 is flattened, after which the inner convex lens 8 are formed. Further, the tops of the inner convex lens 8 are flattened by a first flattening film 9, after which a color filter layer 10 is formed, further flattened by a second flattening film 11, and microlenses 12 formed thereafter. Reference numeral 14 indicates a pad part. With such a technique, it is said, the inner convex lens 8 can be formed with precision, enabling the light collecting efficiency to be increased without substantially reducing sensitivity.
A description is now given of an instance in which a solid-state image sensing device having a light-shielded area on an edge part of the photoelectric converter element is designed on the basis of Japanese Patent Application Laid-Open No. 2005-012189, with reference to FIG. 16.
FIG. 16 shows a sectional view of the edge of a solid-state image sensing device including a light-receiving area and a light-shielded area. In FIG. 16, reference numeral 101 indicates a light-shielded area pixel, 102 indicates a light-receiving area pixel, 103 indicates photosensitive areas (photoelectric converter elements), 104 indicates a first metal wiring layer, 105 indicates a second metal wiring layer, and 106 indicates a third metal wiring layer that blocks incoming light. Most of the photoelectric converter elements 103, the first metal wiring layer 104, the second metal wiring layer 105 and the third metal wiring layer 106 are physically and electrically separated from each other by interlayer dielectrics, with portions connected by contact plugs and via plugs. It should be noted that the pixel shielded from incoming light by the third metal wiring layer 106 becomes the light-shielded area pixel, with the third metal wiring layer 106 configured so as not to intrude upon the light-receiving area pixel 102. In addition, reference numeral 112 indicates a flattening film that covers the height difference created by the third metal wiring layer 106, and is formed so as to provide a uniform surface for the formation of inner lenses 108 described later. Reference numeral 107 indicates a passivation layer and 108 indicates the inner lenses. After formation of the inner lenses 108, a flattening film 109 is formed to attain a flat surface, on which a color filter layer 110 is. Thereafter further flattening is performed using flattening layer 109 is further formed to attain a flat surface, on which microlenses 111 are formed.
However, as shown in FIG. 16, if the solid-state image sensing device is configured using the technique shown in FIG. 15, the distance from the light-receiving surface to the bottom of the inner lenses lengthens, and conversely light collecting efficiency worsens.